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| Joined: | 04-16-2018 |
| Location: | Santa Barbara, California USA |
| Posts: | 22 |
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It's been awhile since I posted to this string. I have continued to fiddle with things and took the car to someone with more knowledge of Delortos in the meantime. Still not where I need to be, though.
I hope someone can answer a question about A/F meters. I gave up on my first meter, an Innovate Motorsports LM-2 because it kept freezing after a few minutes, and went with an AEM 30-0300 X-Series. Can someone tell me their experience of how stable the reading should be? Mine jumps so much I have difficulty guessing at an average. Seems like there should be a setting to damp the reading.
Near as I can tell, my A/F readings are
1000 rpm 13.2
2000 rpm 17.5
3000 rpm 16.5
4000 rpm 16.0
5000 rpm 14.0
so idle looks OK (adjusted that using the screws - approximately 4 turns out), and using 7850.8 and 55 tube and jet.
Looks like it jumps to very lean, and then drops down to reasonable at higher rpm. Is that controlled by the emulsion tube? Currently 7772.8 and 170. I did not see this before the last carb expert made some changes. It was the same main emulsion tube but 160 jet. At that time A/F was pretty consistent at 13.5 to 12.1.
Mainly I am wondering if the readings are real, but I suspect so as I think I am getting spitting at the 2000 - 4000 range.
BTW - I have a Carb-Tune Pro, and check it often for balance.
Hi Don,
Assuming that your AFR monitor is accurate and was properly free-air calibrated, and based on the popping/spitting in the RPM range where the idle circuit transitions to main, it seems like your 55 idle jets might be on the lean side. I know that you had 62s before, which do seem a bit rich, but it is probable that your hot-rod 2.2 with cams flows a decent amount of air, and thus needs more fuel to match.
My J-H engine is still a stock 2.0L with stock cams, but has Dellorto 45s and pretty much mirrors the Lotus "Spec 5" in every category including compression and port size, and the jetting is very close to that. We have 58 idle jets, which might seem a bit rich, but the engine runs happily and the spark plugs don't load up (I have delayed the installation of an AFR gauge because the engine runs so well). Early on we had an issue with the idle jets becoming restricted with debris from the tank, and when this would happen, the engine would pop/hesitate in the 3000-4000 range but otherwise run well above and below that. The jets were not completely plugged, but restricted and thus mimicked smaller jets; cleaning them out cured this every time, and once we ran all of the junk out of the fuel tank and changed the fuel filters again, this has not been an issue since.
I'd say make sure your idle jets are clear and try 58s with the same jet holders/emulsion tubes. Make only one change at a time and document any differences in running/AFR.
Let us know what you find out.
Chris